Question

At push-off phase during walking, the anterior/posterior ground reaction force at the center of pressure is 157 N and the vertical ground reaction force under the right foot is 293 N. The foot has a length of 0.3 m and is 33 degrees above the ground. The center of pressure is located under the metatarsal heads.

Calculate the moment arm for the anterior/posterior ground reaction force. (m)

Calculate the moment arm for the vertical ground reaction force. (m)

Calculate the torque generated by the anterior posterior ground reaction force about the ankle. (Nm)

Calculate the torque generated by the vertical ground reaction force about the ankle. (Nm).

Calculate the total torque generated by the ground reaction force about the ankle. (Nm)

Answer 1

(a) For moment arm of anterior/posterior ground reaction force, the feet is at angle of 33 degrees and length is 0.3m

i.e hypotenuse is 0.3 m and angle between base and hypotenuse is 33 degrees. Thus the perpendicular distance can be found as

(b) For vertical force, moment arm is

(c) Torque generated by anterior/posterior ground reaction force = Force * moment arm

= 157 * 0.16 = 25.65 Nm

(d) Torque generated by vertical ground force = 293 * 0.25 = 73.72 Nm

(e) Total torque = Sum of torque due to anterior / posterior ground force and Torque due to vertical Ground reaction force = 25.65 + 73.72 = 99.37 Nm